I've had problems installing XP and Vista in both 32 bit and 64 bit flavors. Once thing you should try is going to planetamd64.com and checking for the latest and greatest verified working nVidia floppy disk drivers. They don't all work the way they're supposed to.
Something I had to do to get Windows to boot at all was to disable the Silicon Image RAID card on my machine through the install and after the first boot. I also have to go into the boot settings in the BIOS and tell it to boot to the nVidia RAID first, or the multi(0)rdisk(0)disk(0)etc..etc.. settings aren't correct.
I've got an ASUS A8N SLI Deluxe, which is of course not the same, but it sounds like we've got a lot of the same parts. PlanetAMD64 has a great deal of information, even motherboard specific information. You might check it out.